The present invention generally relates to computer chip manufacture, and more particularly to processing techniques for manufacturing MIM structures on semiconductor substrates.
Capacitors are comprised of two metal plates separated by an insulator material. These devices are used extensively in circuitry formed in semiconductor substrates. The typical process for formation of capacitors is by deposition of a metal layer, deposition of an insulator layer, deposition of a second metal layer, and finally etching the three layer structure to create capacitors at desired locations. This requires extensive use of lithographic masking, does not flow well with complementary metal oxide semiconductor (CMOS) processing, and may not be practicable in some damascene applications.
It is an object of this invention to provide a low cost and efficient process for manufacturing metal insulator metal capacitor (MIM cap) structures in semiconductor substrates.
According to the invention, a first metal layer is deposited within a cavity in a substrate. The substrate may be silicon, gallium arsenide or some other material, but also may be a silicon dioxide layer, or an alternative insulative layer of a semiconductor device (such as would be the case in damascene processing). Regardless of the nature of the substrate, for purposes of this invention the substrate will be deemed any material used in semiconductor fabrication. After depositing the first metal layer, the top surface is oxidized to form a metal oxide over coat layer. Oxidation can be best achieved by anodizing. Once the metal oxide over coat layer is formed, additional insulative layers may be added such as silicon nitrides and silicon oxides (e.g., silicon dioxide), or a second metal layer can be deposited directly on top of the metal oxide over coat layer. Preferably, the first and second metal layers are the same; however, they could be different to meet the requirements of the component being manufactured. A significant number of variations on these processes can be employed.